[QE-users] 回复: Difference between pw.x and cp.x for relax, ve-relax calculation

[likejiang at ustb.edu.cn]

Dear Giuseppe,

Thanks for your kind explanation.

As per your suggestion, it might be better to do 'vc-relax'/'relax' only
with pw.x, while do CPMD only with cp.x. But we should try to keep the
parameters (such as, nspin, tot_magnetization, lda_plus_u, Hubbard_U(i),
degauss, smearing, ...) being the same for the same materials while dong
'vc-relax'/'relax' with pw.x and CPMD with cp.x. 

I will do more test and let you know if any progress/problem.

Thanks.
Kejiang

-----邮件原件-----
发件人: users-bounces at lists.quantum-espresso.org
<users-bounces at lists.quantum-espresso.org> 代表 Giuseppe Mattioli
发送时间: 2022年4月7日 18:22
收件人: users at lists.quantum-espresso.org
主题: Re: [QE-users] Difference between pw.x and cp.x for relax, ve-relax
calculation


Dear Kejiang
As a very general rule, partially depending on the history of the codes
included in the QE distribution, pw.x is the "engine" for electronic
structure calculations (including geometry and cell optimizations, but also
Born-Oppenheimer MD simulations), and cp.x the "engine" for Car-Parrinello
ab initio molecular dynamics simulations.  
A very high degree of interoperability between the two codes has been
achieved in more recent years, but as a useful rule of thumb it is still
sensible to perform your calculations using the designated code.

Regarding the main parameters, of course using the same pseudopotentials
with the same ecutwfc and ecutrho is a good starting point, but there are
tips and tricks that depend on your actual setup.
HTH
Giuseppe

Quoting likejiang at ustb.edu.cn:

> Dear QE-Users,
>
> In QE 7.0, I noticed that the calculation choice for cp.x can also be 
> 'relax', 'vc-relax', 'scf', and 'nscf' which are the key functions of
pw.x.
> But the other parameters in cp.x are far less than the pw.x, for 
> instance, it is known that K point cannot be set in cp.x.
>
> Could anyone help to explain the difference between pw.x and cp.x for 
> 'relax', 've-relax' calculation.
>
> Because I am trying to do some CPMD simulation which can only be done 
> with cp.x, I hope to use cp.x for 'relax' and 'vc-relax' calculation 
> to keep the consistence of parameters in the whole process.
>
> Any comments or suggestions will be much appreciated.
>
> All the best,
> Kejiang
>
> -------------------------------------------------
> Dr. Kejiang Li
> School of Metallurgical and Ecological Engineering, University of 
> Science and Technology Beijing Xueyuan Rd., Haidian District, Beijing 
> 100083, P. R. China https://kejiangli.com/



GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.mattioli at ism.cnr.it>

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